As the value and use of information continues to increase, individuals and businesses seek additional ways to process and store information. One option available to users are information handling systems. An information handling system generally processes, compiles, stores, and/or communicates information or data for business, personal, or other purposes, thereby allowing users to take advantage of the value of the information. Because technology and information handling needs and requirements vary between different users or applications, information handling systems may also vary regarding what information is handled, how the information is handled, how much information is processed, stored, or communicated, and how quickly and efficiently the information may be processed, stored, or communicated. The variations in information handling systems allow for information handling systems to be general or configured for a specific user or specific use such as financial transaction processing, airline reservations, enterprise data storage, or global communications. In addition, information handling systems may include a variety of hardware and software components that may be configured to process, store, and communicate information and may include one or more computer systems, data storage systems, and networking systems, e.g., computer, personal computer workstation, portable computer, computer server, print server, network router, network hub, network switch, storage area network disk array, RAID disk system and telecommunications switch.
Storage area network and server systems using redundant array of independent disks (RAID) have been effectively using Serial Attached SCSI (SAS) (SCSI is an abbreviation for “Small Computer System Interface”) for transfer of data and control information among the various disk drives and computer servers. SAS offers full duplex, dual-ported serial connections that support the most stringent of high-availability requirements. SAS uses point-to-point serial connections that may be easily scalable for high-speed shared bandwidth connections by integrating the multiple-ported serial connections on a very large scale integrated circuit (VLSI) device.
The disks in the storage area network and server systems have to be polled to discover disk events. Polling of the disks is preferably done when the disks are idle, e.g., not being accessed, or when executing a time consuming background task such as disk self test (DST). Overhead due to disk polling is tolerable when the number of disks is relatively small. However, for an information handling system with a relatively large number of disks, polling may negatively impact the performance of the information handling system and may increase design complexity thereof.
Currently, an asynchronous event notification (AEN) transaction cannot be initiated by a SAS target device, e.g., disk. SAS is based on the third generation architectural model for SCSI devices (SAM-3). Older SCSI systems before SAM-3 had the concept of asynchronous event reporting (AER). For example, the MRIE (method of reporting informational exceptions) bit in the information exceptions mode page in SPC-2 (SCSI primary Commands—2) had one of the settings as AER. Present technology AEN transactions take up valuable time slots in the in-band communications protocols of information handling systems.